The dramatic increase in the population of Latinos-the largest minority group in the U.S.-over the last decade and challenges Latinos face in terms of accessing health care in the U.S. make it imperative to develop a clear understanding of the factors and issues that affect Latino health disparities in the U.S. Our long term goal is to contribute to the reduction, prevention, and eventually elimination of Latino health disparities, especially those in HIV/AIDS and substance abuse. The objectives of the proposed P20 Center of Excellence-NCMHD Center for Substance Use and HIV/AIDS Research on Latinos in the U.S. -are: (1) Conducting original research exploring the role of behavioral and social factors contributing to or influencing minority health and health disparities;(2) Translating research findings into effective interventions for improving minority health or eliminating health disparities;(3) Conducting original research exploring the efficacy of a full range of health promotion and information dissemination approaches for improving minority health or eliminating health disparities;(4) Establishing innovative partnerships between academic institutions and community groups/organizations;and (5) to increase the number of researchers and professionals who are committed to eliminating health disparities, especially those from minority and medically under-served populations. The proposed Center will expand the activities of two R24 Centers of Excellence in Florida International University (FIU), the largest four-year Hispanic Serving Institution in the U.S. It will build on an existing collaboration between FIU and two community-based organizations: SPECTRUM, the oldest and largest non-profit substance abuse treatment agency in South Florida, and Miami Behavioral Health Center, the largest provider of behavioral healthcare services to Latinos in Florida. The Center will be organized around four cores: administrative, research, research education/ training, and community engagement/outreach. Its study population will be the Latino population in Miami-Dade County, the only county in the U.S. with an immigrant majority, 97 percent of which are Latinos. The contributions of the Center are significant, since the Center will fill in the need to conduct research that bridges HIV/AIDS and substance use, enhance trust between the researchers and the community, and produce a cadre of scientists conducting research on health disparities-especially those from Latino and other minority and medically under-served populations. Relevance to Public Health: The Center is expected to lead to development and refinement of culturally relevant and evidence-based HIV prevention strategies available to HIV-uninfected/ infected individuals and users of substances among the Latinos, who are disproportionately affected by the HIV/AIDS and substance abuse epidemics in the U.S.